I. Field
The present invention relates generally to communication, and more specifically to techniques for transmitting data in a wireless communication system.
II. Background
Wireless communication systems are widely deployed to provide various communication services such as voice, packet data, multi-media broadcast, text messaging, and so on. These systems may be multiple-access systems capable of supporting communication for multiple users by sharing the available system resources. Examples of such multiple-access systems include Code Division Multiple Access (CDMA) systems, Time Division Multiple Access (TDMA) systems, Frequency Division Multiple Access (FDMA) systems, and Orthogonal Frequency Division Multiple Access (OFDMA) systems. A CDMA system may implement Wideband CDMA (W-CDMA), cdma2000, and so on. W-CDMA is described in documents from a consortium named “3rd Generation Partnership Project” (3GPP). cdma2000 is described in documents from a consortium named “3rd Generation Partnership Project 2” (3GPP2). 3GPP and 3GPP2 documents are publicly available.
W-CDMA and cdma2000 employ direct sequence CDMA (DS-CDMA), which spectrally spreads a narrowband signal over the entire system bandwidth with a spreading code. DS-CDMA has certain advantages such as ease of supporting multiple access, narrowband rejection, and so on. However, DS-CDMA is susceptible to frequency selective fading, which causes intersymbol interference (ISI). A complicated receiver with an equalizer may be needed to combat the intersymbol interference.
A wireless communication system may send multicast and broadcast transmissions that are variable in nature. A multicast transmission is a transmission sent to a group of terminals, and a broadcast transmission is a transmission sent to all terminals within a broadcast coverage area. For example, the multicast and broadcast transmissions may have variable data rates that change over time. Furthermore, the number of transmissions and/or the types of transmissions to be sent may change over time. For this system, it is challenging to allocate and utilize the available system resources for the transmissions in an efficient manner.
There is therefore a need in the art for techniques to send variable transmissions in a wireless communication system.